1. Field of the Invention
This invention pertains generally to application of a priming compound to a surface, and more particularly to application of a primer for the pretreatment of surfaces upon which an elastomeric gasket is to be molded in situ and adhered to the primed surface.
2. Description of the Prior Art
The invention is particularly adapted for the production of glazing units or window assemblies for automotive vehicles, although it will find utility generally in a great many other fields. Installation of fixed window units in earlier automotive vehicles generally involved manual installation of the glazing unit using suitable mechanical fasteners such as metal clips for securing the unit in the vehicle body, applying sealant around the marginal edges of the glazing unit, and positioning decorative trim strips around the unit to cover the junction between the marginal edges of the glazing unit and the adjacent portions of the vehicle body. Assembly and installation of such units was relatively slow and costly inasmuch as a considerable amount of labor was required. The procedure was not readily adaptable to being speeded up to accommodate increased automobile production line rates, nor was it adapted to being automated.
Efforts to overcome these disadvantages resulted in numerous improved window structures. Thus, unitary window assemblies were developed wherein a sheet of glass was provided with an adjacent peripheral frame, with a casing or gasket of molded material extending between the frame and the peripheral margin of the window to hold the glass sheet within the frame. Fasteners provided at spaced locations along the frame permitted the entire assembly to be guided into position over an appropriate opening in a vehicle and secured to the vehicle as a unit. Such unitary window units reduce the time required and simplify installation in the vehicle opening. However, due to the labor required in manually assembling the frame and gasket on the sheet of glass, the structures are relatively costly.
More recently, in order to eliminate the manual assembly, so-called encapsulated glazing units have been developed wherein individual sheets of glass or laminated glass units are formed with integral frame or gasket members molded and cured in situ by a reaction injection molding (RIM) process. One such process and resulting product is shown and described in U.S. Pat. No. 4,561,625 to Weaver commonly assigned with the instant application. Such encapsulating glazing units can be fabricated with a minimum of hand labor, and the resulting units can be readily attached to the portions of the vehicle body defining the window openings during assembly of the vehicle.
As described in the aforementioned patent, such encapsulated units are fabricated by disposing a predetermined portion of the marginal periphery of a sheet of transparent material within a mold structure. A polymeric gasket forming material is injected into the mold cavity and cured in situ on the sheet to encapsulate the marginal peripheral edge portion of the sheet. The resulting assembly can then be readily attached to the body portion defining the periphery of a window opening during manufacture and assembly of a vehicle.
Due to the nature of the glass surfaces, it is known that the gasket materials may not form a permanent, long term bond directly to the glass. Thus, they may not maintain adhesion to the glass surface for a length of time consistent with the life of the automobile. Exposure to weather moisture and sunlight, as well as other factors, may cause the gasket material to loosen from the glass with the passage of time, and ultimately to separate entirely from the glass. In order to improve the adherence of the gasket material to the glass and increase the service life of the encapsulated units to an acceptable level, it has been common practice to apply a coating of a liquid primer material to the affected surface of the glass prior to formation of the gasket thereon. Heretofore, this has been accomplished as by manually painting a band of the primer material along the appropriate edge portion of the glass panel. Such a procedure may, for example, utilize a brush periodically dipped in a container of the primer material, or a plastic squeeze bottle containing the primer material and having a suitable dispensing tip. In any event, the procedures are not entirely satisfactory in that they are time-consuming, labor-intensive and may not result in a satisfactory coating of the primer material. Thus the primer layer, which is generally a urethane material, should be applied as a uniform, continuous, relatively thin band in order to function properly. Should the layer be of excessive thickness, it may separate within the layer along a cleavage plane, resulting in failure of the bond. Of course, if the layer is not of sufficient thickness or if certain areas are not coated, the primer layer would likewise be ineffective for its intended purpose. The primer, and particularly the solvent therefore, may be toxic in nature so that manual application thereof, particularly when using an open container of the primer, may require use of protective equipment by the workers. Such manual application procedures also generally result in waste of the primer material and generally messy conditions in the work place. Due to the difficulty in controlling the width of manually applied bands, it may also be necessary to mask the workpiece prior to application of the primer material.
Thus, as will be readily apparent, the existing procedures for applying primer material to the edges of sheet material are not entirely satisfactory, and there is a need for a system for efficiently applying a band of primer of a desired uniform thickness and width to such sheet material.